Heating of yarns by passing the yarns over a roller has been practiced in the art for some time. It has been known to provide various means of rotation for the rollers, including roller bearings, spindle bearings, point bearings of precious minerals, as well as forced air bearings.
It has also been known to provide a temperature gradient across the transverse face of a roller heater. Until the present invention, however, it has not been possible to spin polymers satisfactorily at high speeds -- above 2000 meters per minute -- and pass the spun product over a heated roller and obtain uniform results.